Revert "md: add md_submit_discard_bio() for submitting discard bio"

This reverts commit 2628089.

Matthew Ruffell reported data corruption in raid10 due to the changes
in discard handling [1]. Revert these changes before we find a proper fix.

[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1907262/
Cc: Matthew Ruffell <matthew.ruffell@canonical.com>
Cc: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

drivers/md/md.c

@@ -8582,26 +8582,6 @@ void md_write_end(struct mddev *mddev)
 
 EXPORT_SYMBOL(md_write_end);
 
-/* This is used by raid0 and raid10 */
-void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
-			struct bio *bio, sector_t start, sector_t size)
-{
-	struct bio *discard_bio = NULL;
-
-	if (__blkdev_issue_discard(rdev->bdev, start, size,
-		GFP_NOIO, 0, &discard_bio) || !discard_bio)
-		return;
-
-	bio_chain(discard_bio, bio);
-	bio_clone_blkg_association(discard_bio, bio);
-	if (mddev->gendisk)
-		trace_block_bio_remap(bdev_get_queue(rdev->bdev),
-			discard_bio, disk_devt(mddev->gendisk),
-			bio->bi_iter.bi_sector);
-	submit_bio_noacct(discard_bio);
-}
-EXPORT_SYMBOL(md_submit_discard_bio);
-
 /* md_allow_write(mddev)
  * Calling this ensures that the array is marked 'active' so that writes
  * may proceed without blocking.  It is important to call this before

drivers/md/md.h

@@ -713,8 +713,6 @@ extern void md_write_end(struct mddev *mddev);
 extern void md_done_sync(struct mddev *mddev, int blocks, int ok);
 extern void md_error(struct mddev *mddev, struct md_rdev *rdev);
 extern void md_finish_reshape(struct mddev *mddev);
-extern void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
-			struct bio *bio, sector_t start, sector_t size);
 
 extern bool __must_check md_flush_request(struct mddev *mddev, struct bio *bio);
 extern void md_super_write(struct mddev *mddev, struct md_rdev *rdev,

drivers/md/raid0.c

@@ -477,6 +477,7 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 
 	for (disk = 0; disk < zone->nb_dev; disk++) {
 		sector_t dev_start, dev_end;
+		struct bio *discard_bio = NULL;
 		struct md_rdev *rdev;
 
 		if (disk < start_disk_index)
@@ -499,9 +500,18 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 
 		rdev = conf->devlist[(zone - conf->strip_zone) *
 			conf->strip_zone[0].nb_dev + disk];
-		md_submit_discard_bio(mddev, rdev, bio,
+		if (__blkdev_issue_discard(rdev->bdev,
 			dev_start + zone->dev_start + rdev->data_offset,
-			dev_end - dev_start);
+			dev_end - dev_start, GFP_NOIO, 0, &discard_bio) ||
+		    !discard_bio)
+			continue;
+		bio_chain(discard_bio, bio);
+		bio_clone_blkg_association(discard_bio, bio);
+		if (mddev->gendisk)
+			trace_block_bio_remap(bdev_get_queue(rdev->bdev),
+				discard_bio, disk_devt(mddev->gendisk),
+				bio->bi_iter.bi_sector);
+		submit_bio_noacct(discard_bio);
 	}
 	bio_endio(bio);
 }